1. Field of the Invention
The present invention relates to a thin-film magnetic head, head gimbal assembly, hard disk drive, and magnetoresistive device for reading magnetic information from a hard disk or the like by utilizing a magnetoresistance effect.
2. Related Background Art
Various studies have recently been under way in order to realize higher sensitivity in thin-film magnetic heads (see, for example, Japanese Patent Application Laid-Open No. 2002-232035, No. 2003-8108 and No. 2002-157711). Japanese Patent Application Laid-Open No. 2002-232035 discloses a specular head improved upon a spin valve head. This specular head utilizes specular reflection at the interface between a very thin oxide layer (NOL: Nano Oxide Layer) and a metal layer, so as to increase further the resistance change. Japanese Patent Application Laid-Open No. 2003-8108 discloses a technique in which a current restriction layer comprising electrically insulating and conductive parts mixed with each other is disposed on the upper or lower face of a free magnetic layer, so as to improve output signal. Japanese Patent Application Laid-Open No. 2002-157711 discloses a technique in which a ferromagnetic layer on the free side (free layer), a nonmagnetic intermediate layer, a ferromagnetic layer on the fixed side (pinned layer), and an insulating layer are disposed in this order, so as to improve reproduction output.